Malnutrition often accompanies chronic illness in childhood in the US. Poor nutritional status is thought to compromise the metabolic response to infection. In the US it is difficult to delineate the metabolic consequences of malnutrition during infection because there are very few children with primary malnutrition. In Malawi, where primary malnutrition is prevalent, the nutritional effects on metabolism during infection can be headily studied. We will study 3 groups of children age 12-60 months, those with marasmus and acute infection, those who are well-nourished with acute infection and those with marasmus without infection. In these 3 groups of children we will measure whole-body and splanchnic bed protein kinetics, total energy expenditure, the magnitude of the acute phase response, and the pro-inflammatory cytokine response to characterize and compare the metabolic response to infection. This proposal will also compare nitrogen conservation and the acute phase response in two diets with differing amino acid compositions, milk and egg white-tryptophan. Hypercortisolemia is typically seen in malnutrition, yet the metabolic response to cortisol is blunted from that which occurs in well-nourished children. Thus, we will also explore the glucocorticoid receptor response to endogenous hypercortisolemia by measuring the number, isoform type and cellular location of the glucocorticoid receptors. These studies are essential to developing rational dietary recommendations for the many chronically ill children with protein-energy malnutrition in the US.